Multiple DHCP'd addresses on one NIC

[Aleksandar Milivojevic]

Jeff Vian wrote:

> Maybe someone with definitive information can chime in here, but AFAIK
> an IP is tied to the adapter by MAC address..  Unless you have a device
> with a different MAC address it always seems to get just one IP no
> matter how many times you make a lease request.

I believe this is the way Shaw Cable works.  They tie IP address to  MAC 
address.  Also, if you do reverse lookup of your dynamic IP address, 
you'll see that they also dynamically update their DNS with something 
like this:

s0106004f4e138bf8.wp.shawcable.net

004f4e138bf8 is MAC address of my ethernet card.  Wp is for Winnipeg. 
Don't know what s0106 is, but it seems to never change.

So basically, you get kind-of free basic dynamic DNS service.  "Kind-of" 
since TTL is one day (real dymanic DNS services usually have TTL set to 
several minutes or less, depending on how much you pay).  Not really a 
big problem if you are at Shaw, since the address you get assigned at 
Shaw almost never change (as long as your lease dosn't expire).  Mine 
hasn't changed for almost a year.  The only gotcha is, if you change 
NIC, your name will change too.  I solved this by having 
www.milivojevic.org (my private web site) be CNAME to the Shaw assigned 
name.  So if I change my NIC, I'll simply change CNAME record to point 
to new name.

I simply love Shaw because of this small features (that casual users 
will never notice).

My guess is, with Shaw he'll need one MAC address per IP address.  A hub 
(or switch) with cable modem and several NICs connected to it should do 
the trick.

If you need all this for business, having static IP addresses isn't that 
expensive either.  2 static IP addresses are additional $20/month (but I 
think you need to have at least SOHO package to be able to add static IP 
addresses, which is $65/month, and includes email and web hosting, and 
registration of one domain).

-- 
Aleksandar Milivojevic <amilivojevic at pbl.ca>    Pollard Banknote Limited
Systems Administrator                           1499 Buffalo Place
Tel: (204) 474-2323 ext 276                     Winnipeg, MB  R3T 1L7